This invention relates to a surface acoustic wave apparatus constructed by sealing a chip-shaped surface acoustic wave element into a package and a method of manufacturing the surface acoustic wave device.
As is generally known, the face-down bonding technique has been put to practical use as one of the techniques for putting various chip-shaped electronic part elements, including semiconductor elements, into a package or the like.
The face-down bonding technique is a packaging technique where the connection terminals provided on a package are connected to the connection terminals of an electrode pattern provided on one surface of the chip element by means of conductive bumps. The term face-down bonding comes from the fact that the surface on which the electrode pattern of the chip element has been formed is caused to face the package.
A surface acoustic wave apparatus, which is constructed by applying the face-down bonding technique to surface acoustic wave elements of chip-shaped electronic part elements, has been available in various configurations shown in FIGS. 4 to 7.
FIG. 4 shows a configuration where the electrode pattern 3a of a surface acoustic wave element 3 is face-down bonded to the mounting surface 1a of the concave-shaped base 1 via conductive bumps 2 and then a flat-plate-like cap 4 is put on the base 1.
FIG. 5 shows a configuration where the electrode pattern 3a of a surface acoustic wave element 3 is face-down bonded to the mounting surface 1a of the concave-shaped base 1 via conductive bumps 2 and then a concave-shaped cap 4 is put on the base 1.
FIG. 6 shows a configuration where the electrode pattern 3a of a surface acoustic wave element 3 is face-down bonded to the mounting surface 1a of the flat-plate-like base 1 via conductive bumps 2 and then a concave-shaped cap 4 is put on the base 1.
FIG. 7 shows a configuration where the electrode pattern 3a of a surface acoustic wave element 3 is face-down bonded to the mounting surface 1a of the flat-plate-like base 1 via conductive bumps 2 and then the surface acoustic wave element 3 is resin-sealed with a cap 4 made of mold resin.
In recent years, surface acoustic wave apparatuses, particularly mobile radio communication filters, have been required to have a low-loss, high-attenuation frequency characteristic. Additionally, as the apparatuses have been getting smaller, the filter parts have also been required to decrease in size.
In addition to this, for example, in cellular phones or the like, a very large number of parts have been used and each part has been required to keep a high quality level. They have particularly been required to have a high reliability under the mechanical stress of impact, falling, vibration, or the like, or the thermal stress of temperature changes (widening the using temperature range).
However, with the configurations of the conventional surface acoustic wave apparatuses shown in FIGS. 4 and 5, since the surface acoustic wave element 3 is housed inside the concave-shaped base 1 and the top surface of the surface acoustic wave element 1 is located lower than the top surface of the base 1, this causes the following problems.
First, in a die shear strength test by which the junction of the conductive bumps 2 is checked by pressing the surface acoustic wave element 3 sideways along the mounting surface 1a of the base 1, the clearance between the side face of the surface acoustic wave element 3 and the inner wall surface of the base 1 is so narrow that it is difficult to insert a test jig for pressing the surface acoustic wave element 3 into the clearance, which makes the examination difficult.
Furthermore, when the surface acoustic wave element 3 is removed from the base 1 and fault analysis is performed, the clearance between the side face of the surface acoustic wave element 3 and the inner wall surface is so narrow that it is difficult to insert tweezers for taking out the surface acoustic wave element 3 into the clearance, which makes it difficult to take the surface acoustic wave element 3 out of the base 1. This makes the fault analysis difficult.
Additionally, when the surface acoustic wave element 3 is mounted on the base 1, the sucker of a collect is caused to adhere to the surface acoustic wave element 3 by suction and the element 3 is inserted into the base 1. Because the sucker of the collect also needs to go into the inside of the base 1 when the surface acoustic wave element 3 is inserted into the inside of the base 1, only the sucker of the collect narrower than the inner length, or width, of the base 1 can be used.
In the examination, measurement, or fault analysis described above, because only the sucker of the collect narrower than the inner length, or width, of the base 1 can be used, excessive force can be exerted on the surface acoustic wave element 3, which is therefore liable to break.
Since the conventional surface acoustic wave apparatus shown in FIG. 6 uses the flat-plate-like base 1, the following problems arise: when the base 1 is joined to the cap 4 with solder or adhesive, the solder or adhesive squeezed from between the base 1 and the cap 4 is liable to flow toward the conductive bumps 2.
Furthermore, since the mounting surface 1a to which the conductive bumps 2 are connected and metallize are formed on the same surface of the flat-plate-like base 1, the flatness of the metallize joined to the cap 4 is degraded, which causes a hermetic sealing problem. In addition, because the base 1 takes the form of a flat plate, alignment is difficult when the base is jointed to the cap 4.
The conventional surface acoustic wave apparatus shown in FIG. 7 has not only the problem caused by the configuration of the surface acoustic wave apparatus of FIG. 6 but also an aging problem. Specifically, since the stress of mold resin is exerted on the surface acoustic wave element 3, the stress makes the surface acoustic wave element 3 liable to age.
It is, accordingly, an object of the present invention to overcome the above problems by providing not only a high-quality surface acoustic wave apparatus which enables a surface acoustic wave element mounted on the base to be subjected easily to such processes as examination, measurement, and fault analysis, but also a method of manufacturing the same.
A surface acoustic wave apparatus according to the present invention comprises a surface acoustic wave element, a base having a mounting surface on which the surface acoustic wave element is mounted and a side wall surrounding the surface acoustic wave element, and a cap so joined to the base that it covers the surface acoustic wave element, wherein the side wall of the base is formed lower than the highest part of the surface acoustic wave element.
With the above configuration, because the side wall of the base is formed lower than the highest part of the surface acoustic wave element mounted on the mounting surface, that is, because the highest part of the surface acoustic wave element mounted on the mounting surface is raised above the side wall of the base, the surface acoustic wave element mounted on the base can be subjected easily to, for example, examination, measurement, fault analysis, and others. Therefore, it is possible to provide a high-quality surface acoustic wave apparatus.
The base is composed of an almost flat-plate-like base body with a mounting surface on which the surface acoustic wave element is mounted and a frame member so provided on the mounting surface of the base body that it surrounds the surface acoustic wave element. The height of the side wall can be set easily by selecting the frame member.
The frame member is constructed by stacking plural frame member layers. The height of the wall surface can be set easily by selecting the number of frame member layers or a combination of frame member layers differing in thickness.
The cap is formed into an almost concave shape and joined to the frame member of the base by using the portions projecting from the side wall of the base of the surface acoustic wave element as a guide, thereby housing the surface acoustic wave element together with the base. The positioning for junction can be done easily using the portions projecting upward from the side wall of the base as a guide.
The difference in height between the height of the side wall of the base and the highest part of the surface acoustic wave element mounted on the mounting surface of the base is set at about 50 xcexcm or more. This makes it possible to easily engage, for example, a test jig or the like with the portions projecting upward above the side wall of the base for examination. Thus, the setting is practical.
The surface acoustic wave element has one surface on which an electrode pattern is formed and is mounted in such a manner that the electrode-pattern-formed surface faces the mounting surface of the base. This enables face-down bonding.
The electrode pattern of the surface acoustic wave element is connected electrically to the mounting surface of the base via conductive bumps. This enables the surface acoustic wave element to be mounted easily.
A method of manufacturing surface acoustic wave apparatus according to the present invention comprises the step of, when a cap is jointed to a base having a mounting surface on which a surface acoustic wave element is mounted and a side wall surrounding the surface acoustic wave element in such a manner that it covers the surface acoustic wave element, making the side wall of the base lower than the highest part of the surface acoustic wave element mounted on the mounting surface.
With this method, because the side wall of the base is formed lower than the highest part of the surface acoustic wave element mounted on the mounting surface, that is, because the highest part of the surface acoustic wave element mounted on the mounting surface is raised above the side wall of the base, the surface acoustic wave element mounted on the base can be subjected easily to, for example, examination, measurement, fault analysis, and others. Therefore, it is possible to provide a method of manufacturing high-quality surface acoustic wave apparatuses.
The base is composed of an almost flat-plate-like base body with a mounting surface on which the surface acoustic wave element is mounted and a frame member so provided on the mounting surface of the base body that plural frame member layers are stacked so as to surround the surface acoustic wave element and that the height of the side wall of the base is set by stacking the frame member layers. This enables the height of the side wall to be set easily by selecting the number of frame member layers or a combination of frame member layers differing in thickness.
Furthermore, when cap is joined to the base, the positioning is done using the portions projecting from the side wall of the base of the surface acoustic wave element as a guide. This enables the cap to be joined to the base easily.